EU-1 is a high activity aluminosilicate zeolite catalyst (U.S. Pat. No. 4,537,754) having 10-ring pores and high internal volume. It is useful as a catalyst and sorbent and shows interesting shape selectivity (U.S. Pat. No. 4,537,754; Sovererijns et al, Microporous Materials, 4, page 123 (1995)). Its compositional variations include the replacement of Al by Ga, Fe or B. As the acidity of these different metal (M) forms decreases in the order Al, Ga, Fe, B, reactions requiring the lowest acidity, such as paraffin isomerization, are probably best carried out with the borosilicate form or those materials having high Si/M ratios (i.e., lower number of acid sites). Unfortunately, when made at the higher silica ratios (those greater than about 40) some EU-1 materials have poor sorption capacity after removal of the templates normally used in its synthesis) resulting in poor accessibility of reactants and low catalytic reactivity. This may be caused by partial framework collapse (reflected in deteriorating X-ray diffraction evidence) or trapped detrital material blocking the pores (indicated by stable X-ray diffraction profiles but inferior n-hexane sorption capacities). Evidence seems to point to the latter cause in these subject materials and may be inherent to the high silica synthesis process, which requires excess silica in the mother liquor, resulting in entrainment, primarily, of siliceous species within the zeolite structure. In constrained pore systems such as EU-1, a small amount of detritus may readily block major parts of the accessible structure. Whilst it is well known that post acid treatments or chemical treatments with complexing agents may restore structural accessibility in some zeolites, including EU-1, in this case, such treatments would tend to remove the framework boron, or other M entities, responsible for the desired selective catalytic activity.